Presently, I am using stock Message app(Lineage 14.1, System app). Now, I have installed and made Google Messenger as default app(installed from Play Store). When a message is received, a message notification is displayed(Google Messenger). I opened Google messenger app and deleted that message. But, while I opened stock message app, the deleted message still visible. Why is this so?
This is possibly because when a message comes in to your phone it is caught by both applications and saved. The data is duplicated across both applications and if you delete from one it is not deleted from the other. If you do not wish to use the reinstalled messaging app you cad either remove its privileges or force stop it.
After few hours of observations, it came to know that, clearing ram usage of both apps, makes both of them with equal number of messages. Actually, messages received on android device is stored on a database, which requires a
root to explore. And, this database is actually fetched to both applications.